First implementation of K2V (#293)

**Specification:**

View spec at [this URL](https://git.deuxfleurs.fr/Deuxfleurs/garage/src/branch/k2v/doc/drafts/k2v-spec.md)

- [x] Specify the structure of K2V triples
- [x] Specify the DVVS format used for causality detection
- [x] Specify the K2V index (just a counter of number of values per partition key)
- [x] Specify single-item endpoints: ReadItem, InsertItem, DeleteItem
- [x] Specify index endpoint: ReadIndex
- [x] Specify multi-item endpoints: InsertBatch, ReadBatch, DeleteBatch
- [x] Move to JSON objects instead of tuples
- [x] Specify endpoints for polling for updates on single values (PollItem)

**Implementation:**

- [x] Table for K2V items, causal contexts
- [x] Indexing mechanism and table for K2V index
- [x] Make API handlers a bit more generic
- [x] K2V API endpoint
- [x] K2V API router
- [x] ReadItem
- [x] InsertItem
- [x] DeleteItem
- [x] PollItem
- [x] ReadIndex
- [x] InsertBatch
- [x] ReadBatch
- [x] DeleteBatch

**Testing:**

- [x] Just a simple Python script that does some requests to check visually that things are going right (does not contain parsing of results or assertions on returned values)
- [x] Actual tests:
  - [x] Adapt testing framework
  - [x] Simple test with InsertItem + ReadItem
  - [x] Test with several Insert/Read/DeleteItem + ReadIndex
  - [x] Test all combinations of return formats for ReadItem
  - [x] Test with ReadBatch, InsertBatch, DeleteBatch
  - [x] Test with PollItem
  - [x] Test error codes
- [ ] Fix most broken stuff
  - [x] test PollItem broken randomly
  - [x] when invalid causality tokens are given, errors should be 4xx not 5xx

**Improvements:**

- [x] Descending range queries
  - [x] Specify
  - [x] Implement
  - [x] Add test
- [x] Batch updates to index counter
- [x] Put K2V behind `k2v` feature flag

Co-authored-by: Alex Auvolat <alex@adnab.me>
Reviewed-on: https://git.deuxfleurs.fr/Deuxfleurs/garage/pulls/293
Co-authored-by: Alex <alex@adnab.me>
Co-committed-by: Alex <alex@adnab.me>

1 files changed, 158 insertions, 0 deletions

diff --git a/k2v_test.py b/k2v_test.py
new file mode 100755
index 00000000..3219056e
--- /dev/null
+++ b/k2v_test.py
@@ -0,0 +1,158 @@
+#!/usr/bin/env python
+
+import os
+import requests
+from datetime import datetime
+
+# let's talk to our AWS Elasticsearch cluster
+#from requests_aws4auth import AWS4Auth
+#auth = AWS4Auth('GK31c2f218a2e44f485b94239e',
+#                       'b892c0665f0ada8a4755dae98baa3b133590e11dae3bcc1f9d769d67f16c3835',
+#                       'us-east-1',
+#                       's3')
+
+from aws_requests_auth.aws_auth import AWSRequestsAuth
+auth = AWSRequestsAuth(aws_access_key='GK31c2f218a2e44f485b94239e',
+        aws_secret_access_key='b892c0665f0ada8a4755dae98baa3b133590e11dae3bcc1f9d769d67f16c3835',
+        aws_host='localhost:3812',
+        aws_region='us-east-1',
+        aws_service='k2v')
+
+
+print("-- ReadIndex")
+response = requests.get('http://localhost:3812/alex',
+                        auth=auth)
+print(response.headers)
+print(response.text)
+
+
+sort_keys = ["a", "b", "c", "d"]
+
+for sk in sort_keys:
+    print("-- (%s) Put initial (no CT)"%sk)
+    response = requests.put('http://localhost:3812/alex/root?sort_key=%s'%sk,
+                            auth=auth,
+                            data='{}: Hello, world!'.format(datetime.timestamp(datetime.now())))
+    print(response.headers)
+    print(response.text)
+
+    print("-- Get")
+    response = requests.get('http://localhost:3812/alex/root?sort_key=%s'%sk,
+                            auth=auth)
+    print(response.headers)
+    print(response.text)
+    ct = response.headers["x-garage-causality-token"]
+
+    print("-- ReadIndex")
+    response = requests.get('http://localhost:3812/alex',
+                            auth=auth)
+    print(response.headers)
+    print(response.text)
+
+    print("-- Put with CT")
+    response = requests.put('http://localhost:3812/alex/root?sort_key=%s'%sk,
+                            auth=auth,
+                            headers={'x-garage-causality-token': ct},
+                            data='{}: Good bye, world!'.format(datetime.timestamp(datetime.now())))
+    print(response.headers)
+    print(response.text)
+
+    print("-- Get")
+    response = requests.get('http://localhost:3812/alex/root?sort_key=%s'%sk,
+                            auth=auth)
+    print(response.headers)
+    print(response.text)
+
+    print("-- Put again with same CT (concurrent)")
+    response = requests.put('http://localhost:3812/alex/root?sort_key=%s'%sk,
+                            auth=auth,
+                            headers={'x-garage-causality-token': ct},
+                            data='{}: Concurrent value, oops'.format(datetime.timestamp(datetime.now())))
+    print(response.headers)
+    print(response.text)
+
+for sk in sort_keys:
+    print("-- (%s) Get"%sk)
+    response = requests.get('http://localhost:3812/alex/root?sort_key=%s'%sk,
+                            auth=auth)
+    print(response.headers)
+    print(response.text)
+    ct = response.headers["x-garage-causality-token"]
+
+    print("-- Delete")
+    response = requests.delete('http://localhost:3812/alex/root?sort_key=%s'%sk,
+                            headers={'x-garage-causality-token': ct},
+                            auth=auth)
+    print(response.headers)
+    print(response.text)
+
+print("-- ReadIndex")
+response = requests.get('http://localhost:3812/alex',
+                        auth=auth)
+print(response.headers)
+print(response.text)
+
+print("-- InsertBatch")
+response = requests.post('http://localhost:3812/alex',
+                        auth=auth,
+                        data='''
+[
+    {"pk": "root", "sk": "a", "ct": null, "v": "aW5pdGlhbCB0ZXN0Cg=="},
+    {"pk": "root", "sk": "b", "ct": null, "v": "aW5pdGlhbCB0ZXN1Cg=="},
+    {"pk": "root", "sk": "c", "ct": null, "v": "aW5pdGlhbCB0ZXN2Cg=="}
+]
+''')
+print(response.headers)
+print(response.text)
+
+print("-- ReadIndex")
+response = requests.get('http://localhost:3812/alex',
+                        auth=auth)
+print(response.headers)
+print(response.text)
+
+for sk in sort_keys:
+    print("-- (%s) Get"%sk)
+    response = requests.get('http://localhost:3812/alex/root?sort_key=%s'%sk,
+                            auth=auth)
+    print(response.headers)
+    print(response.text)
+    ct = response.headers["x-garage-causality-token"]
+
+print("-- ReadBatch")
+response = requests.post('http://localhost:3812/alex?search',
+                        auth=auth,
+                        data='''
+[
+    {"partitionKey": "root"},
+    {"partitionKey": "root", "tombstones": true},
+    {"partitionKey": "root", "tombstones": true, "limit": 2},
+    {"partitionKey": "root", "start": "c", "singleItem": true},
+    {"partitionKey": "root", "start": "b", "end": "d", "tombstones": true}
+]
+''')
+print(response.headers)
+print(response.text)
+
+
+print("-- DeleteBatch")
+response = requests.post('http://localhost:3812/alex?delete',
+                        auth=auth,
+                        data='''
+[
+    {"partitionKey": "root", "start": "b", "end": "c"}
+]
+''')
+print(response.headers)
+print(response.text)
+
+print("-- ReadBatch")
+response = requests.post('http://localhost:3812/alex?search',
+                        auth=auth,
+                        data='''
+[
+    {"partitionKey": "root"}
+]
+''')
+print(response.headers)
+print(response.text)